Скалиола: Мәрмәрге ұқсас әсем жабын техникасы

Type of fine plaster

Scagliola (from the Italian scaglia, meaning "chips") is a type of fine plaster used in architecture and sculpture. The same term identifies the technique for producing columns, sculptures, and other architectural elements that resemble inlays in marble. The scagliola technique came into fashion in 17th century Tuscany as an effective substitute for costly marble inlays, the pietra dura works created for the Medici family in Florence. The use of scagliola declined in the 20th century. Scagliola is a composite substance made from plaster of Paris, glue and natural pigments, imitating marble and other hard stones. The material may be veined with colors and applied to a core, or desired pattern may be carved into a previously prepared scagliola matrix. The pattern's indentations are then filled with the colored, plaster like scagliola composite, and then polished with flax oil for brightness, and wax for protection. The combination of materials and technique provides a complex texture, and richness of color not available in natural veined marbles. A comparable material is terrazzo. Marmorino is a synonym, but scagliola and terrazzo should not be confused with plaster of Paris, which is one ingredient.

Batches of pigmented plaster, modified with animal glue are applied to molds, armatures and pre plastered wall planes in a manner that accurately mimics natural stone, breccia and marble. In one technique, veining is created by drawing strands of raw silk saturated in pigment through the plaster mix. Another technique involves trowelling on several layers of translucent renders and randomly cutting back to a previous layer to achieve colour differential similar to jasper. When dry, the damp surface was pumiced smooth, then buffed with a linen cloth impregnated with Tripoli (a siliceous rottenstone) and charcoal; finally it was buffed with oiled felt; beeswax was sometimes used for this purpose. Because the colours are integral to the plaster, the pattern is more resistant to scratching than with other techniques, such as painting on wood. There are two scagliola techniques: in traditional 'Bavarian scagliola' coloured batches of plaster of Paris are worked to a stiff, dough like consistency. The plaster is modified with the addition of animal glues such as isinglass or hide glue. 'Marezzo scagliola' is worked with the pigmented batches of plaster in a liquid state and relies mainly on the use of Keene's cement, a unique gypsum plaster product in which plaster of Paris was steeped in alum or borate, then burned in a kiln and ground to a fine powder; invented around 1840, it sets to an exceptionally hard state. It is typically used without the addition of animal glues. Marezzo scagliola is often called American scagliola because of its widespread use in the United States in the late nineteenth and early twentieth century. Slabs of Marezzo scagliola may be used as table tops. When set, scagliola is hard enough to be turned on a lathe to form vases, balusters and finials.